The present invention relates to a spool assembly and more particularly to a spool assembly of the type having a hollow exterior tube to which end flanges are secured by fasteners retained in interior slots formed in projections on the exterior tube.
Conventional spool assemblies have solid cylindrical bodies that result in relatively expensive and heavy constructions, and because of their weight they demand relatively high power input and must be carefully balanced for effective application to a winding operation.
To avoid the disadvantages of solid spool assembly constructions, various hollow spool assemblies have been designed including those disclosed in Markle Canadian Patent No. 460,596, issued Oct. 25, 1949, Jones U.S. Pat. No. 3,614,018, issued Dec. 29, 1969, and Hutchinson U.S. Pat. No. 3,650,494, issued Mar. 21, 1972, all of which have either a central core or end plugs of special construction for primary attachment thereto of screws that have secondary threaded engagement in an exterior shell. A hollow tube construction is also shown in Clinton U.S. Pat. No. 2,225,551, issued Dec. 17, 1940, which shows solid ribs without slots, which ribs require precision machining of screw holes to align with the screw holes in the flanges in contrast to a fully extrudable tube with screw receiving slots extruded therein and accommodating some misalignment as in the present invention; further the Clinton patent discloses screw holes disposed so that the screws bite into the tube wall itself weakening the tube rather than being spaced from the wall as is possible with the present invention. The spool assembly of my aforementioned co-pending U.S. Patent Application Ser. No. 391,555 represents an improvement over these prior hollow spool assemblies in that it provides a lightweight, yet structurally strong, spider-shaped core on which an exterior tube is supported in a manner that does not require threaded screw engagement with the tube. On the other hand, the present invention provides a spool assembly wherein the end flange attachment is made in a unique manner directly to the exterior tube, with end reinforcement being provided if desired. Thus, the present invention also provides a spool assembly that is lightweight and inexpensive, and yet has necessary strength characteristics.